3DS is an 8th gen system so yes.

Not until the NGP says so!

I voted yes.

If you want to make a distinction between handhelds and consoles, fair enough, but either way the first new-gen system was released yesterday.  It does not belong to the current-gen of anything.

To cater towards more market segments. To cater towards an audience that prefers playing on the go, than at home. 

Handhelds are just portable consoles to me, and that was they will always be. With that said, yes I do believe this is the 8th generation. 

I believe the 3DS has started the 8th Gen too, but they each cater to different market segment: home console and handheld. 

That might have been true before the DS and PSP but meany Games that are on both DS and PSP might have originally been put on Home Console eg DQIX, VC2 and VC3, The 3rd Birthday and MGS PW. so they are competing for the same marketshare SONY and NINTENDO are backing both there Handhelds Consoles and Home Consoles pretty much equally at the moment it's a case of not Putting all your eggs in on basket so to speak.     

If the 8th gen started it started with On Live not the 3DS

you are thinking of Japan which gone handheld, but does not applies anywhere else. And by your thinking the Wii is in major trouble now that the 3ds is out.

Outside of the fanbase community and within the actual market, the PSP2/NGP and 3DS are absolutely considered part of the 8th generation of videogaming. Historically, gaming's generations ARE indeed tied to their console releases, yes. But while that's the predominantly leading factor of each generation, that doesn't mean the generations START with the home consoles.

The DS is 100% officially considered part of the seventh generation. Yet it released more than a full year before any of the home consoles did. That doesn't discount its ties to the seventh gen, however. Generations don't end as soon as their successors start, after all, so why do people care so much, anyways? The 3rd gen was still fully supported by its leading manufacturer until 2002 - during the sixth generation's heyday. And said sixth generation is still living pretty well right now with the PS2. All a new generation means is that we have new hardware that is a clear succession to the old, and will serve to compete against a different set of hardware. The DS competes against the Wii, PS3, and 360. The 3DS, while it will at first, will mostly be competing against their successors.

It is most definitely an 8th generation device.

As for handheld generations, Mattel's LCD games and the Game and Watch series are the 1st generation of handhelds, which belonged to the 2nd (Atari 2600 era) and 3rd (NES) generations  of videogames (mostly the 2nd).

The Game Boy and Game Gear made up the 2nd generation, which belonged to the 4th gen of gaming (SNES-era).

Third gen consisted of the SEGA Nomad, WonderSwan, Neo Geo Pocket, Game.com (man I wanted one of those so bad back in the day, too!), and Game Boy Color. They fit under gaming's 5th gen (N64, PS1, SAT).

Handheld's fourth gen was a minor one. It had many contenders, but nothing major happened. It had the Game Boy Advance, the N-GAGEs, SwanCrystal, Neo Geo Pocket Color, and a couple others, and it fit under gaming's sixth gen.

Then came the fifth gen - which pretty much was just characterized by the NDS and PSP. There were a couple other contenders, but they were extremely mediocre in comparison. And it obviously fit under the seventh gen of consoles/gaming.

So, naturally, a handheld that drastically outmaneuvers the other handhelds altogether forms a new generation. And since that generation of handhelds was directly tied to a certain generation of gaming altogether, it fits into a new generation of gaming, too.

This, exactly.

For me it has to be a home console.